The bulk material recovered in ore or salt mines can be hauled from the working spaces to the surface by self-propelled trackless vehicles, usually center pivot dumpers.
Such vehicles can be driven by diesel engines although the use of diesel engines for driving the hauling vehicles results in considerable pollution of the underground air.
For this reason it is known to use railbound underground vehicles, which are supplied with electric power via a contact wire extending along the bed or from replaceable batteries.
"CIM Reporter", Vol. 7, No. 2, of May 4, 1981, discloses a center-pivot-steered underground vehicle which is provided with an electric motor and powered from a supply system consisting of a sliding contact line, a current collector and a cable reel. The cable is self-tensioning the vehicle can move along and transversely to the sliding contact line. The cable reel is a random-winding reel, which is rotatably mounted on a horizontal axis and is disposed in front of the vehicle.
German Patent Publication DE-AS No. 25 17 836 discloses means for transmitting electric power by means of a cable from a stationary installation to a vehicle, which may be trackless and is provided with a cable reel unit having a vertical axis on which two concentric drums are rotatably mounted one over the other.
In one embodiment the reel unit is connected to a movable current collector, which moves along a conductor rail system. The power supply cable, e.g. a ribbon cable, and a rope are wound in mutually opposite senses on respective reels.
During transverse movements of the vehicle under the rail system the two drums rotating in mutually opposite senses are intended to prevent an undesired twisting of and interference between the cable and the rope.
That known vehicle has several disadvantages and does not meet the requirement that it should be virtually freely movable and rotatable in any position under the contact wire system through an angular range from 0 to 360 degrees. Because the supply cable itself cannot be rotated as desired, mechanical tensile stresses, ruptures and disruptive electric discharges can easily occur. In most cases the supply cable sags and it may be damaged as it is dragged on the floor or chafes on the vehicle.
Other known vehicles of the kind described hereinbefore have disadvantages which include a small range of travel, an excessive unladen weight of vehicles powered by a battery or from a contact wire, susceptibility of rectifier installations to shock and a susceptibility of d.c. drives provided with a collector to moisture and aggressive gases and liquids.